1. Field of the Invention
The present invention relates to a vibration-testing system used in vibration test for a variety of structures and the like.
2. Description of the Related Art
FIG. 23 shows such conventional multiaxial type of a vibration-testing system. The vibration-testing system 81 is composed of a vibration shaker 83 of a hydrostatic bearing type wherein a vibration table 82 is disposed on the top in the substantially central portion of the vibration shaker, a hydraulic pump unit 84 for controlling a variety of hydraulic pressures in the vibration shaker 83, a cooling blower 85 for cooling the vibration shaker 83, and a power amplifier 86 for supplying an electric power to the vibration shaker 83, the hydraulic pump unit 84, and the cooling blower 85, respectively. In the conventional vibration-testing system 81, since it is so constructed that the vibration shaker 83, the hydraulic pump unit 84, the cooling blower 85, and the power amplifier 86 are disposed individually, the power amplifier 86 is connected to the vibration shaker 83, the hydraulic pump unit 84, and the cooling blower 85 through a power supply cable 87. On one hand, the hydraulic pump unit 84 is connected to the vibration shaker 83 through a hydraulic hose 88, while the cooling blower 85 is connected to the vibration shaker 83 through a duct hose 89.
The vibration shaker 83 includes, as is well-known, a horizontal vibration generation section composed of a pair of horizontal vibration shakers for generating vibration along X-direction in a horizontal plane, another horizontal vibration generation section composed of a pair of horizontal vibration shakers for generating vibration along Y-direction perpendicular to the X-direction, and a further vertical vibration generation section for generating vibration along Z-direction in a vertical direction. Furthermore, the vibration shaker 83 is arranged in such that vibration in three axes along the X-, Y-, and Z-directions may be applied to a material to be tested placed on the vibration table 82, whereby vibration test is carried out.
In the case when the horizontal vibration generation section in the above-described X-direction or the horizontal vibration generation sections in the X- and Y-directions are driven to vibrate the vibration table 82, there is a case where a rotational mode M appears (see FIG. 23) in its vibration characteristic. When the rotational mode M appears, there is such a problem that an accelerated velocity due to the rotational mode M appears in the Y- or Z-direction, whereby a correct vibration test cannot be achieved.